Method of coating with lightweight aggregates



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METHOD OF COATING WITH LIGHT WEIGHT AGGREGATES original Filed May 29, 1944 Fm E - Ihvrn'ora' Robert A. Prasser ArThur S. Nid-Ms Patented Jan. 24, 1950 METHOD OF COATING WITH LIGHTWEIGHT AGGREGATES Arthur S. Nichols, Oak Parli, and Robert A. Prosser, Riverside, lll., assignors to The Illinois Clay Products Company, `loliet, Ill., a corporation oi Illinois Original application May 29, 1944, Serial No. 537,947. )Divided and this application January 21, 1947, Serial No. 723,362

4 Claims. i

This invention relates to methods of projecting materials, and among other objects aims to provide a method particularly adapted for handlinfr and projecting light weight cementitious and similar materials.

The nature of the invention may be readily understood oy reference to one illustrative method and the apparatus for performing that method shown in the accompanying drawing.

in said drawing:

Fig. i is a longitudinal cross-section of the apparatus, the iov/er portion of the apparatus comprising the feed tube being shown in small scale;

Fig. 2 is a cross-section taken on the plane 2 2 of Fig. 1;

3 is a section taken on the plane 3-3 of Fig. l;

i is a section taken on the plane @-4 of Fig. l; and

Fig. 5 is a sectional perspective of the water distributing element.

The application of cementitious insulating coatings to hot surfaces such as the walls of open hearth furnaces, soaking pits, etc., presents problems not encountered elsewhere. It is generally desirable to apply insulation to furnace walls after the furnace has been brought to heat in order to avoid cracks which would develop it the cementitious insulation were applied t0 the furnace while cold. The cementitious aggregates are ver light in weight and are not adapted for handling by conventional means. Regardless of the type of mechanical mixing and applyapparatus heretofore available, the low mass of the aggregates in relation to the adhesiveness of the binding substance, has resulted in clogging.

We have discovered va method of mixing the light weicht aggregates with the binding subwhich it is to be applied, which not only avoids clogging but Waste of the material. In the illustrative method the light weight aggregates, for example` exfoliated vermi-culito, are withdrawn in dry condition by suction from its container. Exfoliated vermiculite in granular form is an excel nt refractory, mineral insulating material. It we s about six pounds per cubic foot and may be readily handled by suction. If the binder used include a dry solid ingredient, the latter is preferably previously mixed in dry form with the vermiculite or other aggregate and supplied in cartons or other containers from which it may be sucked as presently described. This avoids any intermediate handling.

" materials into the chamber l2 and gir The dry substances sucked from the container are formed into a fairly compact stream by causing them to pass through a cylindrical bore by which they are coniined into such compact stream, and given sulcient Velocity to carry them to the surface to be coated. As the stream issues from the bore, liquid is added in the form of a circular series of jets or sprays surrounding the stream of aggregates and outwardly converging thereon and mingling therewith at a point beyond the end of the bore, so that the adhesive character. of the cementitious mixture is developed beyond the end of the bore. Thus substantially no liquid contacts with the inner suriace of the bore, and the formation of sticky substances which would eventually cause clogging is thereby avoided.

By the time the cementitious stream reaches the surface it has developed its adhesive or sticky quality. The adhesive strength of the mixture is suiiicient to hold the light weight aggregates from bouncing away from the surface on impact therewith. Thus little cementitious material is Wasted. This is in contrast with the `action of heavy aggregates which have so much kinetic energy that there is insuiiicient cohesive strength in the mixture to hold the particles of aggregates from bouncing free.

Ir" the adhesive substances are in liquid form they may be applied directly through the enveloping series of jets or sprays as aforesaid.

In the dra :ing is illustrated one form of apparatus for performing the aforesaid process. Such apparatus is highly eiiicient in applying insulation of the character described to hot as well as cold surfaces. As here shown, the gun or projector it has a longitudinal bore ll leading from a mixing and aspirating chamber l2. The latter has a terminal 'iitting i3 Yprojecting laterally from the body of the gun, to which is connected a large diameter tube Ill, preferably of flexible character leading to the supply bin or receptacle i5 containing the light-weight insulating aggregates it in dry form.

Suction suicient to draw the dry aggregates through the tube lll into the chamber l2 is developed in this instance by an nozzle il projecting into chamber l2, preferably in alinement with the bore il.V An air hose other conduit is connected to the apparatus by the iitting f8 which includes a manuali; "oerated valve i9 for controlling the air.

The suction created by the jet of traveling through the apparatus draws the lig-.t-\f.feight es thensuicient velocity to travel through the bore and issue from the discharge outlet 20 without laterally dispersing at the outlet. In other Words, the aggregate travels towards the surface to which it is to be applied in a fairly compact stream but without such high velocity as to cause the particles to bounce aWay on striking such surface.

Adjacent the discharge outlet the aggregates are mixed with water or liquid adhesive which is uniformly distributed around and in the stream by a distributor ring 2| containing a plurality of small size orifices 22 leading from an annular distributing passage 23, formed in this instance by a channel on the inside face of the terminal flange 24 and the outer face of the fitting 2l. Water or other liquid is delivered to the distributing passage 23 from a conduit 25 extending longitudinally of the device and connected by means of a valve fitting 26 to a supply hose or other conduit.

The inner face 2'! of the distributor ring is conical in character to provide an expanding terminal orifice leading from the bore El without substantial angular recesses in which material may collect. A clean-out plug 28 facilitates cleane ing the water passages.

The addition of water or other liquid by means of inwardly directed streams adjacent the dis charge orifice assists in preventing lateral travel of the aggregate and serves to confine it in a fairly compact and low velocity stream. The liquid ratio in insulating cement of this character is not particularly critical and may be increased or decreased to secure the most efficient operation and the least Waste of material Without regard to whether there is an excess of liquid. The excess simply evaporatesl without damage to the insulating layer.

We have found that bentonite is an excellent binding substance. It hydrates quickly on contact with Water to provide a very tenacious or sticky wet bond. When the coating dries, the bentonite provides an excellent dry bond. Preferably the bentonite in powdered form is mixed with the vermiculite or other aggregates, thus requiring only the addition of Water from the spray nozzles. In the short interval between application of water and impact with the surface to be coated, the bentonite develops adhesiveness sufcient to bind the aggregates together and to the surface and to prevent the particles of aggregate bouncing away from the surface. The surface may be quite hot, thereby quickly drying off the water, but the bentonite simultaneously develops a dry bond which maintains the coating in place.

This application is a division of our copending application Serial 537,947, filed May 29, 1944, now Patent 2,437,042.

Obviously the invention is not limited to the details of the illustrative method since these may be variously modified. Moreover, it is not indispensable that all features of the invention be used conjointly since various features may be used to advantage in different combinations and subcombinations.

Having described our invention, we claim:

1. The method of coating a surface with light weight insulating aggregate which comprises sucking a dry, loosely packed mixture of said aggregate and bentonite from a source of supply, confining said dry mixture in the form of a continuously moving air-borne stream, projecting said stream out of connement in the form of a free, unconned stream toward the surface to be coated, and simultaneously continuously lntroducing a spray of Water around and into the unconiined stream in sufficient amount and at such distance from said surface that the adhesive characteristics of the bentonite will be de- Veloped before the stream engages said surface.

2. The method of coating a surface with light Weight insulating aggregate which comprises sucking a dry, loosely packed mixture of exfoliated vermiculite and bentonite from a source of supply, confining said dry mixture in the form of a continuously moving air-borne stream, projecting said stream out of confinement in the form of a free, unconflned stream toward the surface to be coated, and simultaneously continuously introducing a spray of Water around and into the unconned stream in suiiicient amount and at such distance from said surface that the adhesive characteristics of the bentonite will be dcveloped before the stream engages said surface.

3. The method of coating a surface with light weight insulating aggregate which comprises sucking a dry, loosely packed mixture of said aggregate and bentonite from a source of supply, confining said dry mixture in the form of a continuously moving air-borne stream, projecting said stream out of connement in the form of a free, unconlned stream toward the surface to be coated, and simultaneously continuously introducing into the unconned stream a plurality of converging' jets of Water from points substantially equidistantly spaced around the stream, the amount of said water and the distance between its point of introduction and the surface to be coated being such that the adhesive characteristics of the bentonite will be developed be fore the stream engages said surface.

Ll. The method of coating a surface with light weight insulating aggregate which comprises sucking a dry, loosely packed mixture of said aggregate and bentonite from a source of supply, confining said dry mixture in the form of a continuously moving air-borne stream, projecting said stream out of confinement in the form of a free, unconiined stream toward the surface to be coated, simultaneously continuously introducing a. spray of water around and into the unconflned stream in sufficient amount and at such distance from said surface that the adhesive charactern istics of the bentonite will be developed before the stream engages said surface, and simultaneously regulating the velocity at which the wet stream engages said. surface so that the impact of the agggregate will be insumcient to overcome the adhesiveness of the bentonite and the aggregate will not bounce away from the surface.

ARTHUR S. NICHOLS. ROBERT A. PROSSER.

REFERENCES CITE?) The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,595,362 Schaefer Aug. 10, 1926 2,076,898 Labus Apr. 13, 1937 2,081,935 Jones June 1, 1937 2,264,108 Anderson et al Nov. 25, 1941 2,333,189 McGrew Nov. 2, 1943 2,374,732 Colburn May 1, 1945 

1. THE METHOD OF COATING A SURFACE WITH LIGHT WEIGHT INSULATING AGGREGATE WHICH COMPRISES SUCKING A DRY, LOOSELY PACKED MIXTURE OF SAID AGGREGATE AND BENTONITE FROM A SOURCE OF SUPPLY, CONFINING SAID DRY MIXTURE IN THE FORM OF A CONTINUOUSLY MOVING AIR-BORNE STREAM, PROJECTING SAID STREAM OUT OF CONFINEMENT IN THE FORM OF A FREE, UNCONFINED STREAM TOWARD THE SURFACE TO BE COATED, AND SIMULTANEOUSLY CONTINUOUSLY INTRODUCING A SPRAY OF WATER AROUND AND INTO THE UNCONFINED STREAM IN SUFFICIENT AMOUNT AND AT SUCH DISTANCE FROM SAID SURFACE THAT THE ADHESIVE CHARACTERISTICS OF THE BENTONITE WILL BE DEVELOPED BEFORE THE STREAM ENGAGES SAID SURFACE. 